Rapid developments of information technology coming one after another cause technical problems that are difficult to solve in the field of computers. An example is the revelation of more and more of computer virus and program bugs. The development and prevalence of network technology gives the spread of computer virus a further boost. Besides, the widespread of computer usage provides many users uninformed about computers opportunities to contact and utilize computers. Due to such users' incorrect handling, the crash of computer systems used by them is inevitable. All these make the management of computers more and more important.
In particular, the currently popular i386-based PC operating systems such as MS Windows are susceptible to virus attack or crash due to deletion of files or formatting of logical disk drives. When the computer system is corrupted, the user usually cannot restart Windows any more or run diagnostics to recover the system. A survey shows that half of IT cost is due to system recovery. Thus, how to protect against such computer disasters is one of the key issues to meet users' requirement and lower IT cost.
To solve the aforementioned problems, the prior art employs such approaches as listed below to store/recover the main operating system when the system crashes or otherwise goes abnormal, e.g. being affected by virus or memory leak.
1. System management application in the main operating system. This technology has some inherent disadvantages since it depends on the main operating system. Therefore, when MS Windows as the main operating system is corrupted, for example, all applications cannot run. Therefore the system management application cannot achieve effective management when big trouble occurs. For example, when Blue Screen of Death happens, no application can be run in a normal way. When the core of Windows or memory is affected by virus, almost all anti-virus software will ask for a reboot from a clean system before they can work successfully.
2. Pre-Windows environment support. There are several approaches to extend the pre-Windows environment:                Recovery/Bootable CD        OS in hidden hard disk partition        BIOS (Basic Input Output System) enhancement applications (e.g. Phoenix Firstware)                    All of these can provide system management functions in a pre-Windows environment. However, the main problem still exists, i.e. the user must reboot the computer, which causes not only a long wait time but also troublesome operations such as closing applications.                        
3. Hypervisor solution. Hypervisor is a virtual simultaneous running mechanism for operating systems. Under such a mechanism, a base operating system virtualizes all hardware resources to run another operating system. Since there are two operating systems running hierarchically, this mechanism will inevitably reduce system performance in a significant way.